1. Technical Field
The present invention relates to an engagement chain built into a driving system for moving an object in parallel with an installation surface. More specifically, the present invention relates to an engagement chain for a driving system for use in manufacturing facilities in various manufacturing fields, transfer facilities in the transportation field, nursing care facilities in the health-care and welfare fields, stage facilities in the performing art filed and the like.
2. Related Art
Driving systems are currently used for lifting an object which needs to be moved such as a heavy load using a pair of engagement chains, which are commonly referred to as chuck chains. The engagement chains engage with each other as the chains are moved up and down. For example, one such engagement chain is shown in Japanese Patent Publication No. 3370928.
As shown in FIGS. 8 and 9, the engagement chain 500 has inner link units which include a pair of front and rear bushes 530 which are press-fitted into a pair of inner link plates 510. Each inner link plate has a hook-like portion 511. A pair of outer link plates 520 are disposed respectively outside the inner link units in a width direction of the chain, herein referred to as the “chain width direction.” The outer link plates 520 each have a pair of front and rear pin holes and a hook-like portion 521.
The engagement chain is built by connecting the large number of inner link units together in a longitudinal direction, hereinafter referred to as the “chain longitudinal direction,” by press-fitting a pair of front and rear connecting pins 531 into the pair of front and rear pin holes of the outer link plates 520 with the front and rear connecting pins 531 extending through the bushes 530 of the inner link units.
Each bushing 530 has a roller 532 fitted around it. The rollers 532 engage with a pair of driving sprockets 501 disposed so as to face to each other, so that when the driving sprockets are driven, the engagement chains 500 are driven so as to integrally engage with an opposing portion of the chain by causing the hook-like portions 511 of the inner link plates 510 and the hook-like portions 521 of the outer link plates 520 to face to each other in the chain longitudinal direction so as to integrate the chain when the chain is driven from a horizontal direction to a vertical direction.
The respective engagement chains 500 are moved as the pair of driving sprockets 501 come into slidable contact with the rollers 532 of the chain which is pressed against a chain guide 502.
One problem with this configuration, however, is that because the rollers 532 transmit the driving force by engaging with the driving sprocket 501, the engagement chains 500 require spaces where the inner and outer link plates 510 and 520 do not exist in order for the driving sprockets to come into contact with the rollers 532. Thus, in order for the driving force to be transmitted to the chain in the chain longitudinal direction, the spaces occupied by the engagement chains 500 has to be relatively large.
The engagement chain 500 also has had a problem when the driving force transmitted from the driving sprocket 501 to the roller 532 is also transmitted to the pair of right and left inner link plates 510 or the outer link plates 520, as the stress is transferred from the roller to the center part of the connecting pin 531. This can result in a large stress and shearing force, causing bending in the connecting pin 531, thus lowering durability of the chain.
Furthermore, the engagement chain 500 has had a problem that because the rollers 532 engage with the driving sprocket 501 by colliding against teeth of the driving sprocket 501 from a radial direction when the driving sprocket 501 is rotated, the engagement chain 500 generates a large engagement noise during driving.
Accordingly, there is a need for an engagement chain whose driving force per occupied space is increased, whose durability is improved by reducing bending stress and shearing force otherwise acting on connecting pins and whose engagement noise during driving is reduced.